A Munster man accused of mailing a pipe bomb that exploded at the East Chicago post office and injured an employee there last month, as well as making threats to another person, is scheduled to appear in federal court Tuesday.

Eric Krieg, 45, of Munster, was charged last week with the knowing possession of a destructive device and with transporting explosive materials. Krieg is scheduled to appear in the Hammond federal courthouse Tuesday morning for a probable cause and detention hearing, court records show.

A pregnant postal worker was injured when a package, addressed to a Hammond city contractor, detonated shortly after 5:30 p.m. Sept. 6, at the post office at 901 E. Chicago Ave., officials said.

A second piece of mail was sent to another person at his Hammond residence Sept. 29, that contained a bullet and a message that read, "The next one will be in the back of your head," court records state.

Prosecutors said Krieg admitted to his role in mailing the items to the two victims last month.

Krieg made an initial appearance in the case Thursday, the same day U.S. Attorney Thomas Kirsch announced Krieg's arrest and charges, and a judge ordered he remain in custody, court records show.

Prosecutors have not commented on a motive, but Hammond Mayor Thomas McDermott Jr. said the crimes were politically motivated.

Krieg sought public office in Lake County in the past, running as a Republican. He lost both times.

During the 2011 Republican primary, Krieg ran unsuccessfully against Dan Dernulc for a seat on the Lake County Council.

Krieg then ran against Democrat George Van Til in a contentious Lake County surveyor's race in 2012. Van Til won, but was later sentenced to 18 months in federal prison for using county resources to run his campaign.

In 2013, Krieg filed a series of complaints against McDermott with the Lake County Board of Elections. All the allegations in those complaints were dismissed by the board.

Dernulc, who is chairman of the Lake County Republican Central Committee, said while Krieg ran as a Republican he was not a part of the formal party.

Krieg was not a member of the core Republican team, Dernulc said, nor was he a member of the Munster precinct organization. Dernulc said he remembered Krieg attending one meeting with a small group of people but he was not involved with the central committee.

"Really, his participation is kind of as an outside party, as a Munster resident," Munster Councilman John Reed, R-1st, said.